Add possibility to lock extension upload
Problem to solve
Prevent upload of new extension versions, if all extension versions are marked as insecure.
Further details
In case all versions of a TYPO3 extension has been marked as insecure, because the extension author did not reply on email from the TYPO3 Security Team, it should be possible to manually define a "upload lock" for an extension. For extensions flagged with the "upload lock", the extension author can not upload a new version of the extension. Instead, a message is shown, that the extension author must contact the TYPO3 security team.
It must be ensured, that the upload using the UI as well as the upload using the TER REST api is prevented for extensions which have been marked with the new property "upload lock".